The lid on the fish tank cover will not cause hypoxia. Although the contact area between water and air is large without a lid, it helps to increase the dissolved oxygen in water, but the lid does not lead to hypoxia. Anoxia in the water body is mainly caused by high breeding density and more feeding bait, which can be oxygenated by filtration and oxygen pump besides reducing the number of breeding and feeding.
1. Floating head: When fish are hypoxic, they often have the performance of floating head. They will be close to the water surface, and their mouths will keep opening and closing at the place where the water surface contacts the air. It should be noted that if there is only one fish floating head, it can not be explained that it is caused by hypoxia, or it may be due to gill disease, but if there are a large number of floating heads, it means that the dissolved oxygen in the water body is too low.
2. Jumping the tank: Some fish will jump the tank when they are lack of oxygen. Generally, it is difficult to happen in a fish tank with a lid. However, if the lid is not added, it may happen. However, it should be noted that the cause of cylinder jump is not necessarily hypoxia, but may also be frightened or not adapted to the new environment.
3. Anorexia: When it is time to feed the fish, if there is no competition after feeding the fish, they all appear to be inactive, indicating that the water body is anoxic. After discovering this situation, it is necessary to oxygenate, so as not to cause the death of fish due to insufficient oxygen for a long time.
